Turn the system off, and hold the d
key while pressing the power button.
This will initialize a LCD Built in Self Test (BIST).
You will hear some beeping, and see flashing color screens. Take note of any lines that may appear. If you see lines in the colored screens, it would indicate there is a problem with your LCD panel itself. If you do not see the horizontal lines in the BIST, but do see them in the system BIOS... it may indeed be a bad video card